Relational Database Design Algorithms Quiz
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Questions and Answers

Which of the following best defines functional dependency?

  • A set of attributes X determines a set of attributes Y if the value of Y determines a unique value for X.
  • A set of attributes X determines a set of attributes Y if the value of X determines a unique value for Y.
  • A set of attributes X functionally determines a set of attributes Y if the value of Y determines a unique value for X.
  • A set of attributes X functionally determines a set of attributes Y if the value of X determines a unique value for Y. (correct)

    • What does the notation X → Y represent in the context of functional dependencies?

  • X and Y are unrelated attributes in the relation instance.
  • Y functionally determines X in the relation instance.
  • X and Y are equivalent attributes in the relation instance.
  • X functionally determines Y in the relation instance. (correct)

    • What is the goal regarding functional dependencies?

  • To identify all possible attribute combinations in a relation instance.
  • To minimize the number of attributes in a relation schema.
  • To create constraints on attribute values in a relation instance.
  • To determine the properties of functional dependencies and find ways to manipulate them. (correct)

    • In what way are functional dependencies derived?

    <p>From real-world constraints on the attributes.</p> Signup and view all the answers

    What does X → Y hold, as per the definition of functional dependencies?

    <p>$ ext{If } t1[X]=t2[X]$, then $t1[Y]=t2[Y]$ for any two tuples $t1$ and $t2$ in any relation instance $r(R)$.</p> Signup and view all the answers

    Explain the concept of functional dependencies and provide an example to illustrate it.

    <p>Functional dependencies refer to the relationship between sets of attributes in a relation. For example, in a relation with attributes A and B, if for every unique value of A, there is only one corresponding value of B, then A functionally determines B. An example could be a relation representing employees, where the employee ID uniquely determines the employee's name.</p> Signup and view all the answers

    What are the inference rules for functional dependencies and how are they applied?

    <p>The inference rules for functional dependencies are used to derive new functional dependencies from the given set of functional dependencies. These rules include augmentation, transitivity, and decomposition. For example, if X → Y and Y → Z, then by transitivity, we can infer X → Z.</p> Signup and view all the answers

    How are sets of functional dependencies proved to be equivalent, and why is this important in database design?

    <p>Sets of functional dependencies are proved to be equivalent by showing that each set implies the other. This is important in database design to ensure that the set of functional dependencies chosen to enforce constraints on the data is minimal and does not contain redundant dependencies.</p> Signup and view all the answers

    Explain the concept of minimal sets of functional dependencies and their significance in relational database design.

    <p>Minimal sets of functional dependencies are the smallest sets of dependencies that still hold all the constraints of the given set of dependencies. They are significant in relational database design as they help in reducing redundancy and anomalies in the database, leading to a more efficient and normalized database design.</p> Signup and view all the answers

    How can functional dependencies be displayed graphically on a relation schema, and why is this visualization useful in database design?

    <p>Functional dependencies can be displayed graphically on a relation schema by using arrows to represent the dependencies between attributes. This visualization is useful in database design as it provides a clear understanding of the dependencies and constraints within the database, aiding in the normalization and optimization of the database schema.</p> Signup and view all the answers

    Functional dependencies are derived from the real-world ______ on the attributes in a database. They specify a constraint on all relation instances and can be displayed graphically on a relation schema as in Figures in Chapter 14. FDs are derived from the real-world ______ on the attributes Copyright © 2016 Ramez Elmasri and Shamkant B. Navathe Slide 15- 4 1.

    <p>constraints</p> Signup and view all the answers

    Functional dependencies are derived from the real-world ______ on the attributes in a database. They specify a constraint on all relation instances and can be displayed graphically on a relation schema as in Figures in Chapter 14. FDs are derived from the real-world constraints on the attributes Copyright © 2016 Ramez Elmasri and Shamkant B. Navathe Slide 15- 4 1.

    <p>constraints</p> Signup and view all the answers

    For any two tuples t1 and t2 in any relation instance r(R): If t1[X]=t2[X], then t1[Y]=t2[Y] X → Y in R specifies a ______ on all relation instances r(R) Written as X → Y; can be displayed graphically on a relation schema as in Figures in Chapter 14. ( denoted by the arrow: ).

    <p>constraint</p> Signup and view all the answers

    For any two tuples t1 and t2 in any relation instance r(R): If t1[X]=t2[X], then t1[Y]=t2[Y] X → Y in R specifies a ______ on all relation instances r(R) Written as X → Y; can be displayed graphically on a relation schema as in Figures in Chapter 14. ( denoted by the arrow: ).

    <p>constraint</p> Signup and view all the answers

    A set of attributes X functionally determines a set of attributes Y if the value of X determines a unique value for Y. Our goal here is to determine the properties of functional dependencies and to find out the ways of ______ them.

    <p>manipulating</p> Signup and view all the answers

    Study Notes

    Functional Dependency Definition

    • Functional dependency is a constraint between two attributes in a relation, where the value of one attribute determines the value of another.
    • The notation X → Y represents a functional dependency, where X is the determining attribute and Y is the dependent attribute.

    Functional Dependency Properties

    • X → Y holds if the value of X determines a unique value for Y.
    • For any two tuples t1 and t2 in any relation instance r(R), if t1[X] = t2[X], then t1[Y] = t2[Y].

    Goal of Functional Dependencies

    • The goal is to determine the properties of functional dependencies and find ways to infer them.

    Inference Rules

    • There are inference rules for functional dependencies, which are applied to derive new functional dependencies from existing ones.

    Equivalent Sets of Functional Dependencies

    • Sets of functional dependencies can be proved to be equivalent, which is important in database design because it allows for the identification of minimal sets of functional dependencies.
    • Equivalent sets of functional dependencies have the same constraints and implications.

    Minimal Sets of Functional Dependencies

    • Minimal sets of functional dependencies are significant in relational database design because they represent the most concise and essential set of constraints.
    • Minimal sets of functional dependencies are useful in database design because they reduce redundancy and improve data consistency.

    Graphical Representation

    • Functional dependencies can be displayed graphically on a relation schema, which is useful in database design because it provides a visual representation of the constraints.
    • Graphical representation of functional dependencies helps in identifying relationships between attributes and in designing databases.

    Derivation of Functional Dependencies

    • Functional dependencies are derived from the real-world constraints on the attributes in a database.
    • Functional dependencies specify a constraint on all relation instances and can be displayed graphically on a relation schema.

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    Test your knowledge of relational database design algorithms by taking this quiz. Learn about further topics in functional dependencies, inference rules, equivalence of sets of FDs, and minimal sets of FDs.

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